All-optical trapping

All-optical trapping of a degenerate Fermi gas has been demonstrated. First created in a magnetic trap (see Physics Today, Physics Today 0031-9228 52 10 1999 17  https://doi.org/10.1063/1.882853 October 1999, page 17 ), a degenerate Fermi gas consists of fermionic atoms—those with an odd total number of protons, neutrons, and electrons—sufficiently dense and cold that only the lowest trap energy levels are occupied. An all-optical trap has previously been used to confine a Bose–Einstein condensate (see Physics Today, Physics Today 0031-9228 54 7 2001 20  https://doi.org/10.1063/1.1397387 July 2001, page 20 and Physics Today 0031-9228 54 9 2001 79  https://doi.org/10.1063/1.1420529 September 2001, page 79 ). Now, using a stable, high-power CO₂ laser, physicists at Duke University have created a kind of “optical bowl” for lithium-6 atoms: Slowly lowering the bowl’s rim permitted the hottest atoms to evaporate. The researchers then adiabatically recompressed the trap to its full depth, which...